The aims of this ongoing project are to monitor patients with phenotypic abetalipoprotinemia to better delineate nutrient transport (fatty acids, vitamin E) and explore the metabolic consequences and compensatory changes which occur in these patients who lack apoprotein B containing lipoproteins from plasma. GRANT M01RR003340461 This protocol examines the clinical and biochemical efficacy of mevinolin (lovastatin) and its effects upon cholesterol and lipoprotein metabolism. A number of patients will be examined on long-term therapy, for a period in excess of four years, to determine the time related effects of such treatment.